Method for producing coated rare earth transition metal alloy powder, and coated rare earth transition metal alloy powder

Abstract

To provide coated rare earth-transition metal alloy powder, having good magnetic characteristics and excellent heat resistance and weather resistance, and a method for producing the same.SOLUTION: A method for producing alloy powder includes: a first step of, when grinding coarse alloy powder in a solvent, adding a phosphate compound to the solvent to obtain fine powder having a surface coated with a phosphate coating; and a second step of subjecting the obtained fine powder to heating treatment to maintain at a predetermined temperature in a dryer thereby obtaining alloy powder coated with a phosphate coating. In the second step, a pressure Pa in the dryer is measured, and, in a stage where a pressure change P (unit: kPa) shown in formula (1) below satisfies x<P (where x is 0.8 kPa or more and 1.2 kPa or less), heat treatment is performed under a reduced pressure atmosphere where oxygen-containing gas is not introduced in the dryer, while in a stage where P≤x is satisfied, oxygen-containing gas is introduced in the dryer to perform heat treatment under an atmosphere with an oxygen partial pressure of 0.1 kPa or more and 5 kPa or less.SELECTED DRAWING: Figure 1